add function to extract templates to library

Likely the most complex element to extract. Appears in mainly two forms:

1. as href of Wikilinks : also has a similar case, where WIKILINK hrefs have Category links - in which case we don't consider those elements as Categories. So, we have to make a decision regarding what can we do about such Template links.
   
2. nested inside data-mw : is complicated to process, due to the asymmetric nature of the data-mw dictionary, JSON decoding errors due to the presence of escape characters, malformed strings, and bad use(single/double) of quotation mark etc.